Has the Conversion of Natural Wetlands to Agricultural Land Increased the Incidence and Severity of Damaging Freezes in South Florida?

Abstract

On several occasions, winter freezes have wrought severe destruction on Florida agriculture. A series of devastating freezes around the turn of the twentieth century, and again during the 1980s, were related to anomalies in the large-scale flow of the ocean-atmosphere system. During the twentieth century, substantial areas of wetlands in south Florida were drained and converted to agricultural land for winter fresh vegetable and sugarcane production. During this time, much of the citrus industry also was relocated to those areas to escape the risk of freeze farther to the north. The purpose of this paper is to present a modeling study designed to investigate whether the conversion of the wetlands to agriculture itself could have resulted in or exacerbated the severity of recent freezes in those agricultural areas of south Florida.For three recent freeze events, a pair of simulations was undertaken with the Regional Atmospheric Modeling System. One member of each pair employed land surface properties that represent pre-1900s (near natural) land cover, whereas the other member of each pair employed data that represent near-current land-use patterns as derived from analysis of Landsat data valid for 1992/93. These two different land cover datasets capture well the conversion of wetlands to agriculture in south Florida during the twentieth century. Use of current land surface properties resulted in colder simulated minimum temperatures and temperatures that remained below freezing for a longer period at locations of key agricultural production centers in south Florida that were once natural wetlands. Examination of time series of the surface energy budget from one of the cases reveals that when natural land cover is used, a persistent moisture flux from the underlying wetlands during the nighttime hours served to prevent the development of below-freezing temperatures at those same locations. When the model results were subjected to an important sensitivity factor, the depth of standing water in the wetlands, the outcome remained consistent. These results provide another example of the potential for humans to perturb the climate system in ways that can have severe socioeconomic consequences by altering the land surface alone.

The Challenges of Remote Monitoring of Wetlands

“…(2) What are the promising new technologies and sensor/multisensor approaches for more accurate and consistent detection of wetlands? (3) Are there studies that demonstrate how remote long-term monitoring of wetland landscapes can reveal changes that correspond with changes in land cover and land use and/or changes in climate?…”

Severe Winter Freezes Enhance St. Louis Encephalitis Virus Amplification and Epidemic Transmission in Peninsular Florida

“…These freezes, especially those recorded in the 1980s, caused citrus tree mortality in counties located in a zone between Orange County to the north and Martin County to the south. These freezes resulted in a southward migration of the citrus industry from the central Florida peninsula into the southern third of Florida (Rogers and Rohli 1991, Miller and Downton 1992, Easterling et al 1999, Marshall and Pielke 2004, Fraisse et al 2006.…”

Using nocturnal water level fluctuations for estimating seepage from stormwater detention systems

“…Till date, the night‐time method has not been used to estimate long term seepage fluxes. Furthermore, no verification of this method has been conducted for systems in sub‐tropical and tropical regions where the zero ET during night‐time does not hold true, especially during the warmer season when latent heat flux in inundated areas during night‐time results in considerable evaporation (Marshall et al ., ). Apart from testing the applicability of nigh‐time method in tropical and sub‐tropical climatic regimes, it is important to verify the estimates from the night‐time method by comparing it with another method.…”